Alright, let's do another approach. Put your 18-200 to 70-200 range and start photographing without the IS turned on. Shoot at f5.6 and compensate for that 1 stop of light you would get with the 70-200 F4L. This will tell you if you're comfortable shooting without IS.


For sports I'm in no doubt that you will enjoy the non-Is version, but I can't tell you if you'd miss the IS for other purposes.


My safest bet would be to buy the 70-200 F4L, save some money(perhaps earn some with your shots) and save it for a better general purpose lens like the Canon 17-55 f2.8 IS USM or the Tamron 17-50 f2.8 or others.


You're gonna want a better general lens eventually, I can promise you that, because after seeing footage of an L-lens your 18-200 will look..."not that great" anymore [:P]